Objective: In previous studies, some brain areas, including parahippocampal gyrus, were suggested to be associated with panic disorder. Both panic disorder and somatoform disorders are associated with anxiety. This study sought to determine if there are shared neural activity underlying panic disorder and undifferentiated somatoform disorder.

Method: Sixteen nonmedicated patients with panic disorder, 16 nonmedicated patients with undifferentiated somatoform disorder, and 10 healthy subjects were scanned between February 2005 and August 2006. Diagnoses were made according to the Korean version of the Structured Clinical Interview for DSM-IV Axis I Disorders, Research Version, Patient/Non-Patient Edition. Regional cerebral perfusion was measured by 99 m-Tc-ethyl cysteinate dimer single photon emission computed tomography (SPECT). Using statistical parametric mapping analysis, we compared the SPECT images between the groups.

Results: Significant hyperperfusion was found at the left superior temporal gyrus and the left supramarginal gyrus in the panic disorder patients when compared to the controls (family-wise error [FWE], P<.001). The somatoform disorder patients showed hyperperfusion in the left hemisphere at the superior temporal gyrus, inferior parietal lobule, middle occipital gyrus, precentral gyrus, postcentral gyrus, and, in the right hemisphere, at the superior temporal gyrus when compared to the controls (false discovery rate [FDR], P<.001). In contrast, significant hypoperfusion was found at the right parahippocampal gyrus in each of panic disorder (FWE, P=.001) and somatoform disorder (FWE, P<.001) groups compared to healthy controls. However, no significant differences were found in regional cerebral perfusion between the 2 disorder groups.

Conclusions: Both panic disorder and undifferentiated somatoform disorder showed hyperperfusion in the left superior temporal gyrus and hypoperfusion in the right parahippocampal gyrus, which suggests that the 2 disorders are likely to share neural activity.